Geopolitical events can have dramatic repercussions on the availability of petroleum exported from the world's petroleum producing nations. It is therefore apparent that industrial as well as developing nations cannot rely on these petroleum producing countries for a consistent and reliable source of petroleum. Likewise, it is becoming increasing more difficult to locate new sources of petroleum and more apparent that there is only a finite quantity of easily accessible petroleum. Green house gases as well as global warming are also of critical importance when considering the impact of new power production and electrical power generation facilities. For these and other reasons as well, petroleum based combustion type power generation is undesirable. Likewise, nuclear energy is thought of by the general public to be highly dangerous, undesirable, wherein the vast majority of people are opposed to the construction of nuclear facilities. In addition, the disposal of spent nuclear fuel also presents numerous problems and challenges in terms of nuclear accidents and potential acts of terrorism. Public opinion concerning nuclear power generation is therefore very negative and makes its utilization politically unacceptable.
The geothermal energy contained within the earth represents an almost infinite amount of potential energy. The ability to extract this energy in an efficient, cost effective and environmentally safe way has to date proven to be a daunting challenge.
Over the course of the last several hundred years, mankind has created numerous subterranean passageways through the earth for the purpose of extracting minerals, and metal ores. In addition to the current active mines there are also numerous abandoned mines located around the world. These abandoned mines are generally unmarked and unsealed from public access. An abandoned mine may well contain an open yet visually obscured hole that could descend tens if not hundreds of feet in depth. They serve no useful purpose and in fact pose a threat to the safety and well being for those who unwittingly approach the area of an abandoned mine.
The use of an abandoned mine for capturing geothermal energy provides an efficient and cost effective way of tapping geothermal energy from the earth while at the same time providing an environmentally friendly solution to an existing public environmental hazard. There are literally hundreds of thousands of abandoned underground mines throughout the world. Their labyrinths of vertical and horizontal shafts descend deeply into the earth, some of them thousands of feet below the surface. Once the desired ore deposits were found—gold, silver, copper, coal other minerals, or even diamonds—great caverns were excavated and the raw materials were extracted from the earth. The ore was hauled to the surface and processed, usually contaminating the water and scarring the surrounding lands. Once the mines had outlived their usefulness, they were just simply abandoned. Many of these mines have been in existence for over 100 years.
According to a study published in 1996 by the US General Accounting Office (Federal Land Management: Information on Efforts to Inventory Abandoned Hard Rock Mines, GAO/RCED-96-30, February 1996), “no definitive inventory is available concerning the number of abandoned hard rock mines located on federal lands.” However one agency estimate cited in the GAO report indicates that there may be over 560,000 abandoned hard rock mines in the US alone (on both public and private land sites). One objective of the 1996 GAO report was to establish the hazards and estimated costs for remediation. To quote from their report, “The problems posed by abandoned hard rock mines can generally be classified as physical safety hazards or environmental degradation. Physical safety hazards, which can lead to human injury or death, may include concealed shafts or pits, unsafe structures, and explosives. Conditions causing environmental degradation may include drainage of toxic or acidic water, which could result in soil and groundwater contamination or biological impacts.”
As for the estimated costs for remediation, the 1996 GAO report says, “No nationwide cost estimate for reclaiming abandoned hard rock mines on federal lands is available. Preparing accurate estimates of the reclamation costs requires detailed assessments, or characterizations, of the sites, involving physical inspection and in-depth evaluation of the problems at each site.” According to the Report, the Bureau of Mines estimates between $4 billion to $35.3 billion to reclaim less than 30,000 sites on Interior and Forest Service lands. The Mineral Policy Center estimates between $33 billion to $72 billion to reclaim the 560,000 sites it projects are in existence nationally, regardless of whether the lands are publicly or privately owned.
Thus, what is needed in the art is a means for converting an abandoned mine into a geothermal source of energy to provide an efficient and cost effective way of tapping geothermal energy from the earth while at the same time providing an environmentally friendly solution to an existing public environmental hazard.